1. Field of the Invention
The present invention relates to a seal device. More particularly, this invention relates to a seal device which is disposed in a mounting portion whose surrounding space is subject to deformation in shape under the influence of external forces, thermal deformation or the like.
2. Description of the Related Art
Related art 1 of the present invention is disclosed in U.S. Pat. No. 6,237,921. This seal ring is disposed in a gas turbine engine. A similar seal ring is also disclosed in U.S. Pat. No. 5,716,052. This seal ring has a “U”-shaped cross-section. The seal ring is mounted in such a location that seal portions of the seal ring perform elastic deformation due to either thermal stress of high temperature combustion gases or pressure or vibration caused by compressed gases which arises in a neighborhood of the combustion gas flow in the turbine engine. Also there is another type of seal ring whose cross-section is “E”-shape and used in a location for high temperature and high pressure such as gas turbine, nuclear related devices or the like.
FIG. 10 depicts a seal ring of the related art 1 as mentioned above. As shown in FIG. 10, the seal ring 120 has “U”-shaped cross-section thereof. Both end portions of the “U”-shaped seal ring 120 define reverse bend portions 132, 132. The seal ring 120 is a two-ply construction consisting of an inner ring 122 and an outer ring 126. Also an inner circumferential portion of the inner ring 122 defines a groove 134.
The seal ring 120 is used to effect a seal against a high pressure turbine nozzle 110 of a gas turbine. The high pressure turbine nozzle 110 retains a plurality of nozzle vanes 112. The nozzle bane 112 is mounted to a radially inner band 116 in an integral manner which is supported by a support flange 118. The seal ring 120 is arranged between the inner band 116 and the support flange 118 in order to bring the inner band 116 of the high pressure turbine nozzle 110 into sealing contact with the support flange 118.
In this high pressure turbine nozzle 110, high temperature combustion gases 114 received from an upstream combustion chamber (not shown) is turned and accelerated through the nozzle vanes 112. The inner band 116 and the support flange 118 start to receive thermal deformation as heating proceeds. The seal ring 120 which is disposed between the inner band 116 and the support flange 118 impaired by the thermal deformation is forced to undergo elastic deformation to an axial direction due to the thermal deformation of the inner band 116 and the support flange 118. Under this circumstance, a contact point 125 of the seal ring 120 which is located at the center of a “U”-shaped bending portion is supported by the support flange 118. This causes the seal ring 120 to have the reverse bend portions 132, 132 brought into contact with the inner band 116 and the support flange 118 and axially extending slots 134, 134, 134 are formed at three locations, which are defined within or between the reverse bend portions 132, 132. Therefore, it becomes increasingly more difficult for the seal surfaces 132A, 132B of the seal ring 120 to achieve a uniform contact force over a wide range of the elastically deformed area.
The inner ring 122 and the outer ring 126 which is mounted on the outer circumference of the inner ring 122 form a double-layer structure in which a problem arises in seal capability at the joint portions which form junctions at the both ends of an annular body as described in related art 1 (not shown). Out of the three open-ended slots 134, 134, 134 with “U”-shaped cross-section, the largest slot 134 formed in the inner circumferential side has its open-ended portion in an opposite direction to the other two small slots 134 which are relatively located to the both sides of the largest slot 134. Thus, for example, when a fluid pressure acts from a certain direction, a sufficient seal performance cannot be expected. Further, presence of the reverse bend portions 132, 132 disposed at the both open-ended portions of the seal ring 120 increases the production cost because of the difficult bending process involved.
FIG. 11 shows a seal ring 200 with an “E”-shaped cross-section. A similar relative art to the seal ring 200 is disclosed related art 2 in U.S. Pat. No. 4,121,843. The seal ring 200 has a cross-section of two fishing-hook like annular seal portions 201, 202 being joined at one end by means of a middle bridge portion 205. A middle groove 210 is formed between the individual annular seal portions 201, 202 after assembly. The annular seal portions 201, 202 have a first elastic portion 201B and a second elastic portion 202B of a semi-circular section, respectively. A first seal surface 201A and a second seal surface 202A are formed near the end portions of the first elastic portion 201B and the second elastic portion 202B, respectively, wherein the first seal surface 201A and the second seal surface 202A come into contact with a mounting component. In this seal ring 200, a distance from the middle bridge portion 205 to the respective first seal surface 201A and the second seal surface 202A is defined as L2.
In the seal ring 200, when the first seal surface 201A and the second seal surface 202A receive action forces thereat, the first elastic portion 201B and the second elastic portion 202B which have a semi-circular section only exhibit small elastic deformation, thus the middle bridge portion 205 performs elastic deformation such that a gap of the middle groove 210 is further narrowed. Presence of the middle groove 210, however, makes it difficult for the elastic deformation force at the middle bridge portion 205 to be delivered to the first seal surface 201A and the second seal surface 202A in a uniformly urging manner. If the gap in the middle groove 21 is further decreased to zero in which the first elastic portion 201B and the second elastic portion 202B are brought into contact with each other, elastic deformation starts to occur at the first elastic portion 201B and the second elastic portion 202B and this elastic deformation rapidly increases the load. Therefore, a seal ring 200 of this type is not suitable for a case in which a mounting slot for mounting the seal ring 200 changes in dimension. Also the bending process in the production of the seal ring 200 involves forming of “E”-shape, which increases the production cost.
The present invention is introduced to resolve the above mentioned problems and the development of necessary technologies associated with the problems have been under way. A primary technical goal which this invention tries to achieve is to provide a seal device which is capable of exhibiting a substantial sealing ability over a wide range of dimensional change in which external forces due to a fluid pressure, heat-induced stress or the like cause dimensional change in the width of a mounting slot for mounting the seal device. Another goal is to simplify the configuration and reduce its production cost. Yet another goal is to make the mounting process of the seal device straightforward and decrease its assembly cost.